1. Industrial Field of the Invention
The present invention relates to a connecting structure of a circuit board, an electro-optical device, electronic apparatus provided with the same, and a manufacturing method for an electro-optical device.
2. Description of the Related Art
An electro-optical device such as a liquid crystal display device employs an integrated circuit (IC) device, on which driving IC components are mounted, to connect its driving circuit to a liquid crystal display (LCD) panel. Typical IC devices used for this purpose include a chip-on-film (COF) type wherein a flexible wiring board using a so-called "tape automated bonding (TAB) package (also known as a tape carrier package (TCP)" is connected to an LCD panel, and a chip-on-glass (COG) type wherein driving IC components are directly connected to a glass substrate. For instance, the wiring board employing the TCP is advantageous in that it is smaller and thinner than other types of packages, which makes it suited for high-density packaging, and the board is flexible to permit itself to be bent for packaging. These advantages allow the wiring board to find applications in a variety of types of electronic apparatus, including electro-optical devices.
Diverse types of terminals for connection to driving ICs are formed on wiring board employing the TCPs (herein after referred to as "TCP boards"). Hence, to configure electronic apparatus or the like, the terminals of a TCP board are electrically connected to the terminals of another circuit board.
In general, the packaging mode as set forth below is used to connect the terminals of the TCP board and the terminals of another circuit board. With a conductive member such as an anisotropic rubber connector provided between the terminals of the TCP board and the terminals of another circuit board, the TCP board and another circuit board are pressed in a connecting direction thereby to press the terminals of the TCP board and the terminals of another circuit board into contact via the conductive member. This accomplishes electrical connection between the terminals of the TCP board and the terminals of another circuit board.
The connecting structure set forth above, however, has been posing a problem since a flexible wiring board such as the TCP board and another circuit board are pushed against each other to bring them into contact so as to enable the electrical connection. More specifically, in a structure or an environment wherein an adequate force for bringing the flexible wiring board and another circuit board into close contact with each other cannot be secured, if the boards are subjected to external forces, especially vibrations or shocks, electrical connection may not be successfully accomplished, resulting in a continuity failure.
Furthermore, if a rubber connector formed of anisotropic conductive rubber is used for connecting a terminal on an electro-optical device, for example, an LCD panel, to a terminal of a flexible wiring board, then a failure of electrical connection may occur if vibrations, shocks, or other types of external forces are applied.
In addition, a dedicated press-in-contact member such as a case must be used to secure a sufficient contact pressure between a terminal of the flexible wiring board and a terminal of another board, adding to the number of components. Furthermore, to use such a press-in-contact member, the flexible wiring board and another circuit board must be compression-bonded by using a pressing jig. Hence, at locations where direct contact pressure cannot be secured, it is impossible to improve the reliability of contact, leading to a continuity failure.
Accordingly, an object of the present invention is to provide: a circuit board connecting structure which enables contact pressure to be secured without the need for employing a special press-in-contact member so as to achieve higher contact reliability in connecting a circuit board such as a flexible wiring board and another circuit board, which can be configured with less components; an electro-optical device; electronic apparatus provided with the same; and a manufacturing method for an electro-optical device.